This invention relates to window insulating units and more particularly to a modular insert unit particularly adapted for use with double-hung windows for increasing the thermal efficiencies of these windows and reducing heat loss.
It has long been known that in older homes the windows and the glass area constitute the single largest areas through which energy is lost to the outside. Older double-hung windows in particular are often ill fitted, worn, and no longer form a tight perimeter seal and many never did in the first instance. When homes were built before the substantial rise in energy costs, it was often more economical to conserve on materials or use less expensive materials. As a result, insulation was used sparingly, if at all, and windows were not provided with proper storm sashes or weatherstripping material. For example, heat loss through a double glass window with an outside temperature of 0.degree. and an inside temperature of 75.degree. F. may be in the order of 155 BTU per hour per square foot. When this is compared with a loss through a R-13 rated wall structure, which may be in the order of 5 BTU per hour per square foot under the same conditions, it will be seen that there exists a need for a low cost product that can be installed at low cost which will convert at least a portion of lossy windows to the equivalent of a high quality wall, and thereby reduce to a substantial extent the overall heat loss and gain from such a building.
Insulating units which are insertable and removable from inside of an existing structure, such as a home, have been suggested as a means by which some or all of the glass area of windows may be covered up and suitably insulated for reducing heat loss and heat gain. However, such prior art units are generally complicated in construction, high in price, or both. Further, many such units do not provide for a vapor barrier nor do they provide structure by which drafts or the like are reduced. They often do not provide for the support of a decorative covering to match curtains or walls or the like, or provide the appearance of a drawn or partially drawn shade to give a natural and comfortable look.